The Supernova Impostor PSN J09132750+7627410 and Its Progenitor

We report the results of our follow-up campaign of the supernova impostor PSN J09132750+7627410, based on optical data covering ∼250 days. From the beginning, the transient shows prominent narrow Balmer lines with P-Cygni profiles, with a blueshifted absorption component becoming more prominent with time. Along the ∼3 months of the spectroscopic monitoring, broad components are never detected in the hydrogen lines, suggesting that these features are produced in slowly expanding material. The transient reaches an absolute magnitude M _r = -13.60 ± 0.19 mag at maximum, a typical luminosity for supernova impostors. Amateur astronomers provided ∼4 years of archival observations of the host galaxy, NGC 2748. The detection of the quiescent progenitor star in archival images obtained with the Hubble Space Telescope suggests it to be an 18-20 M _⊙ white-yellow supergiant.